This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To study the nature and mechanisms of social transfer of information in cooperatively breeding cotton-top tamarins (Saguinus oedipus). Cooperatively breeding primates divide effort between infant care, vigilance, group defense, and foraging. Individuals within groups engage in each of these roles. Successful coordination within group behavior for successful infant care requires clear communication and attention to others. Does this behavioral coordination lead to social facilitation of cognitive skills as well? In cotton-top tamarins (Saguinus oedipus) we have shown that tamarins rapidly demonstrated cooperation when the simultaneous actions of two monkeys were needed to solve a task, but when tested alone, they inhibited responses suggesting an understanding of the cooperative task. In a follow-up study, tamarins continued to cooperate even when an individual did not receive food in a session suggesting reciprocal altruism. A longitudinal study on the relationship between food offering, tolerated begging and infant skill level found adults use special signals in transferring food to infants and withdraw these signals as infants gain competence. We discovered a novel tool-making and tool use behavior seen in a subset of the colony. Some non-tool-using animals acquire the skill through spontaneous observation of mates. We have completed developmental studies on social learning of a novel foraging task and find that adults provide much more information for infants than they do for juveniles and provide no information to each other (as adults) to facilitate social learning. Finally, we have shown long term retention of social learning (up to three years). Collectively, we find an impressive ability for social learning and information transfer in Callitrichids comparable to or even beyond that of great apes. The biological and behavioral mechanisms leading to cooperative care of infants appear to be linked with cognitive skills that are dependent on social interactions. This research relied on WNPRC Library and Information Services. Funding ended just before this reporting period;publications have resulted.